dt-bindings: tegra: pmc: Add Tegra264 compatible

The PMC found on Tegra264 is similar to the version in earlier chips but
some of the register offsets and bitfields differ, so add a specific
compatible string for this new generation.

Acked-by: Rob Herring (Arm) <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Thierry Reding <[e-mail]>

Documentation/devicetree/bindings/arm/tegra/nvidia,tegra186-pmc.yaml

···
       - nvidia,tegra186-pmc
       - nvidia,tegra194-pmc
       - nvidia,tegra234-pmc
+      - nvidia,tegra264-pmc
 
   reg:
     minItems: 4